The professor spoke so fast during the lecture that we couldn’t___________what he said.

The Nuclear Security Summit is an initiative of Mr. Obama, considers nuclear terrorism to be one of the greatest threats to international security.

.My mother ______ live in the country byherself, but now she got used to ______ together with us in the city.

The boy said ________ couldn’t he work out the problem but his teacher didn’t know how to do it

People in Shaanxi are proud of they have achieved in the past ten years